Rectal Leiomyosarcoma Treated With Surgery and Adjuvant Radiotherapy: A Case Report With a Brief Review of Radiotherapy Techniques From a Radiation Oncologist's Perspective.

We report the case of a 58-year-old male who presented with diarrhea, fever, and weight loss, and was ultimately diagnosed with rectal leiomyosarcoma (LMS). During colonoscopy, a 4 cm polypoid mass was observed 6 cm above the anal verge, with characteristics suggestive of a gastrointestinal stromal tumor (GIST). Colorectal magnetic resonance imaging showed about a 4.1 x 3.3 x 3.3 cm-sized pedunculated mass in the mid-rectum with two possible pathologic lymph nodes. A pathological review of colonoscopic biopsy revealed atypical spindle cell proliferation, suggestive of GIST. Based on this, the initial impression of the patient was a GIST, and the patient underwent ultralow anterior resection. Microscopically, there was a proliferation of spindle cells. Immunohistochemical stain showed that tumor cells co-expressed actin, desmin, and caldesmon, whereas S100 protein, CD34, and DOG-1 were negative. Based on these findings, the final pathological diagnosis was LMS. The patient received postoperative adjuvant radiotherapy (RT) at a dose of 54 Gy. To date, the exact role, specific indications, and techniques of RT, including the RT field and dose/fractionation for rectal LMS, have not yet been clearly defined. Herein, we present a case of rectal LMS treated with adjuvant RT, accompanied by a brief review of RT techniques reported to date for this rare entity.